RFR 8142384: New command: /imports, /i which show the list of imported packages or classes, etc...

[ShinyaYoshida]

Hi Robert.

Some of users will want to know what is already imported.
However, there is no way to know that directly(We can see imported items by
/list, but it shows all of the items which are already typed and there are
no imported items which are imported by start-up).

I propose the new command, /imports and /i, to list imported packages or
classes, etc...

Please review my patch.

Webrev: http://cr.openjdk.java.net/~shinyafox/kulla/8142384/webrev.00/
Bugs: https://bugs.openjdk.java.net/browse/JDK-8142384

Regards,
shinyafox(Shinya Yoshida)